I am almost 4years into parenting...
The first bill is some supplies like cribs, dressers, stroller, clothes, bottles, toys and a hole slew of other things like new clothes for Mrs. and the hosptial won't let you leave without a car seat.
Then the second is the delivery bill (for us $5k and 6k for babies and momma) and the change to health insurance to 'Family'.
If you don't have the space an upgraded or larger vehicle might be in the question. Sometimes the smaller cars don't hold the car seats well.
By the time baby is 1 you've invested a lot into odds n ends like baby medicine and things to make dealing with baby easier.
If you need daycare like we do, it's another 10k a year per kid. So here we are easily 40k into this in just the first year of 2 kids lives.
20k*21years = $420,000 per kid. Granted daycare costs decrease, you dont have birthing and labor costs every year, but tax breaks go away and medical bills increase, food bill increases, clothing and discretionary budget increases and then saving for college. Maybe it's not worth it but having someone help me age into old years is priceless.
They are also a ton of work, outside the cost.
Something I willfully signed up for.